Prosthetic foot

ABSTRACT

A stable shock absorbing prosthetic foot that transfers energy between heel strike and toe-off. A toe plate is separated from one or more other plates by a bumper assembly located at each of the toe end and heel end of the foot. Certain embodiments of the shock absorbing foot of the present invention are designed for use with a prosthetic ankle. A torsion adapter may also be used to attach a prosthetic foot of the present invention to the remainder of a prosthesis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/193,240, which was filed on Aug. 18, 2008 and is hereby incorporatedby reference in its entirety.

BACKGROUND

The present invention is directed to shock absorbing prosthetic foot foruse by an amputee. More specifically, the present invention is directedto a versatile and configurable shock absorbing prosthetic foot having anumber of flexible bumper assemblies that allow the damping and energytransfer characteristics of the foot to be easily adjusted.

It is desirable to produce prosthetic feet having the ability to bothabsorb energy during a heel strike of each step, and to efficientlytransfer the energy to the toe of the foot as the step progresses.Ideally, this energy is released at the moment of toe-off to provideenergy for the next step.

During ambulation, the foot initially contacts the ground at the heel.Therefore, particularly during strenuous activities, it is desirable fora prosthetic foot to be capable of absorbing the shock of this heelstrike, and to transfer the absorbed energy to the toe portion of theprosthetic foot for release upon the subsequent toe-off so that therebound energy is maximized.

Various prosthetic feet have been designed with this in mind. However,known energy transferring designs typically suffer from one or moredrawbacks including, but not limited to, bulkiness, complexity, heavyweight, excessive stiffness, inefficient energy transfer, and theinability to properly optimize the dynamic characteristics of the footfor a particular amputee (particularly after the foot has already beenassembled).

Therefore, it is desirable to provide a prosthetic foot which is notsubject to the shortcomings of the prior art. Consequently, the presentinvention is directed to such a prosthetic foot.

SUMMARY OF THE GENERAL INVENTIVE CONCEPT

The present invention is directed to a versatile prosthetic foot thatallows an amputee to maintain balance and stability even whenencountering changes in terrain. The foot preferably allows for somedegree of flexibility, while also absorbing shocks and providingexcellent energy transfer.

A prosthetic foot of the present invention can also absorb energy onheel strike and propel the wearer forward to load the toe of theprosthesis and store energy that is then released for use duringtoe-off. The various plates of such a prosthetic foot are separated bybumper assemblies at both the toe end and heel end of the foot.Preferably, these toe end and heel end bumper assemblies are asseparated as possible so as to provide an increased spring length thatresults in greater shock absorption and improved energy return. Thus, aprosthetic foot of the present invention provides enhanced stability,control and function, and also affords a prosthetist with an opportunityto easily customize a foot for a particular amputee. Particularembodiments of the present invention are designed for use with aprosthetic ankle.

In one exemplary form, a foot of the present invention includes a shankhaving one end adapted for attachment by various techniques to theremainder of a prosthetic leg (e.g., to a knee joint or socket). Theanterior end of the shank is attached to the anterior end of a subjacentfoot plate. Between the shank and foot plate resides a heel spring,which extends rearward and is connected to both the shank and footplate.

A number of bumper assemblies may be used to connect the shank, footplate and heel plate. These bumper assemblies may include a sleeve thatpasses through the shank or heel plate, and receives a specializedshoulder bolt that engages a T-nut assembly located in the foot plate.These sleeves may be comprised of various materials, including bothrigid and elastomeric materials. When a sleeve has elastomericproperties, it may contribute to the shock absorption and/or energyreturn characteristics of an associated foot. A snubber may surround anassociated sleeve such that the snubber is trapped between the shank andfoot plate, or foot plate and heel plate.

Preferably, the shank, foot plate and heel plate are comprised of acomposite material, such as, e.g., carbon fiber. Such materials arestrong while also promoting good energy transfer during heel strike andtoe off. The foot plate is preferably radiused in the heel and toesection to make heel strike and toe off as smooth as possible. Variousnumbers of bumper assemblies may be present, and such assemblies may bedistributed in different patterns so as to maintain separation betweenat least certain components (e.g., plates) of the foot. The bumperassemblies may have different mechanical properties so as to impartshock absorbency and flexibility characteristics most appropriate for aparticular amputee. Preferably, the toe and heel bumper assembliesreside at extreme ends of an associated foot. This allows for aprosthetic foot of the present invention to have an increased springlength, thereby allowing for greater plate flex and, consequently,increased shock absorption and energy return characteristics.

Embodiments of prosthetic foot of the present invention may be adaptedfor use with various prosthetic leg designs. For example, the shank mayhave an elongated vertical portion in typical form, whereas the verticalportion may be truncated or eliminated in low-profile or ultralow-profile forms. In any event, a prosthetic foot of the presentinvention provides an amputee with a versatile, efficient and stablefoundation.

BRIEF DESCRIPTION OF THE DRAWINGS

In addition to the features mentioned above, other aspects of thepresent invention will be readily apparent from the followingdescriptions of the drawings and exemplary embodiments, wherein likereference numerals across the several views refer to identical orequivalent features, and wherein:

FIG. 1 a is a perspective view of one exemplary embodiment of aprosthetic foot of the present invention;

FIG. 1 b is an enlarged detail view of the indicated portion of theprosthetic foot of FIG. 1 a;

FIG. 2 a is a top plan view of the prosthetic foot of FIG. 1 a;

FIG. 2 b is a cross-sectional view taken along line 2 b-2 b of FIG. 2 a;

FIG. 3 is an exploded side elevation view of the prosthetic foot of FIG.1 a;

FIGS. 4 a-4 c illustrate alternate exemplary embodiments of a shank foruse in a prosthetic foot of the present invention;

FIG. 5 a is a perspective view of the prosthetic foot of FIG. 1 a, butshown at a slightly different angle and with an alternate foot plate;

FIG. 5 b is an enlarged detail view of the indicated portion of theprosthetic foot of FIG. 5 a;

FIG. 6 is a perspective view of one exemplary embodiment of a lowprofile prosthetic foot of the present invention;

FIG. 7 is a perspective view of one exemplary embodiment of an ultra lowprofile prosthetic foot of the present invention;

FIG. 8 a is a perspective view of another exemplary embodiment of aprosthetic foot of the present invention, which includes two bumperassemblies in the toe portion;

FIG. 8 b is an enlarged detail view of the indicated portion of theprosthetic foot of FIG. 8 a;

FIG. 9 is a perspective view of yet another exemplary embodiment of aprosthetic foot of the present invention, having a different heel springattachment design;

FIGS. 10 a-10 g depict alternate exemplary embodiments of bumperassemblies that may be included in a prosthetic foot of the presentinvention;

FIG. 11 a is a front elevation view of an exemplary embodiment of atorsion adapter that can be used with a prosthetic foot of the presentinvention;

FIG. 11 b is a side elevation view of the torsion adapter of FIG. 11 a;

FIG. 12 is an exploded view of the torsion adapter of FIGS. 11 a-11 b;and

FIG. 13 is a front elevation view of an alternate embodiment of atorsion adapter that can be used with a prosthetic foot of the presentinvention;

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S)

One exemplary embodiment of a prosthetic foot 5 of the present inventionis illustrated in FIGS. 1-3. As shown, the prosthetic foot 5 includes ashank 10, a foot plate 25, and an intermediary heel plate 30. The shank10 is shown to have an elongated and substantially vertical portion 15that graduates into a slightly curved foot portion 20. The shank 10 isshaped to control spring rate, so as to accommodate amputees ofdifferent weights and activity levels, and also offers dynamic input atboth heel strike and toe off. Depending on the materials selected forits manufacturing, the shank 10 may also permit some degree ofinversion/eversion movements through twisting in the short direction.The height of the vertical section 15 may be adjusted as needed toaccommodate amputees requiring different prosthetic limb lengths.

The foot plate 25 acts as a base that allows an amputee to maintainbalance and stability. Preferably, the foot plate 25 is designed to havesome degree of flexibility, so as to be capable of storing and releasingenergy. The foot plate 25 is preferably designed for installation into afoot shell (not shown) and may be of varying shape. Preferably, however,the foot plate 25 has a curved heel section 25 a and toe section 25 b tohelp promote smooth heel strike and toe off. The curved heel and toesections 25 a, 25 b may also aid in prolonging foot shell life byminimizing or eliminating the possibility of an edge thereof cuttingthrough or puncturing the foot shell.

The heel plate 30 resides between the shank 10 and foot plate 25. Thethickness of the heel plate 30 may be varied to produce different springrates that can be selected according to a given amputee's weight, gaitcharacteristics, and/or activity level. As shown, the heel plate 30 maybe curved to some degree. In this particular embodiment, the curvatureof the heel plate 30 closely tracks the curvature of an underlyingportion of the foot plate 25. However, the heel plate 30 may also haveother curvatures. The heel plate 30 provides for shock absorbency atheel strike, and stores and returns energy during an amputee's gaitcycle. As with the shank 10, the heel plate 30 may also permit acontrolled amount of inversion/eversion movement through twisting. In atleast certain embodiments of the present invention, the heel plate 30may be field serviceable, thereby allowing a prosthetist to easilyinterchange heel plates 30 so as to optimize the foot 5 of the presentinvention for a particular amputee.

In the assembled prosthetic foot 5, the foot portion 20 of the shank 10and the foot plate 25 are connected by a toe bumper assembly 35 at/nearcorresponding toe ends 10 b, 25 b thereof. A forward end 30 b of theheel plate 30 is attached to the underside of the foot portion 20 of theshank 10, rearward of the toe bumper assembly 35. A rearward end 30 a ofthe heel plate 30 is connected by a heel bumper assembly 40 to the heelend 25 a of the foot plate 25.

As can be best observed in FIGS. 1 a and 2 b, assembly of the shank 10,toe plate 25 and heel plate 30 in this manner results in a prostheticfoot wherein both the foot portion 20 of the shank and the heel plateare suspended above the foot plate. As can also be seen, the heel plate30 extends rearward from its connection point with the foot portion 20of the shank 10.

The heel plate 30 may be fastened to the shank 10 using a variety ofdifferent fasteners or other fastening techniques. In one preferredembodiment (best observed in FIG. 3), attachment of the heel plate 30 tothe shank 10 is accomplished by passing a threaded fastener assemblythrough corresponding holes 45, 50 in the foot portion 20 of the shankand the forward end 30 a of the heel plate 30. As shown, the fastenerassembly includes a sleeve 55 that extends into the hole 45 in the shank10 and a T-nut 70 that extends into the hole 50 in the heel plate 30.The sleeve 55 may include a flange 60 that rests on the top surface ofthe shank 10 when the sleeve is installed thereto. A threaded fastener75 passes through the sleeve 55 and threads into the T-Nut 70 in theheel plate 30, thereby securing the heel plate to the shank 10. Thesleeve 55 may include a countersunk neck portion 65, as shown, toreceive a tapered head portion of the threaded fastener 75. In otherembodiments, a flat-head threaded fastener may be used, eliminating theneed for such a countersunk neck portion.

As described above, attachment of the shank 10 and heel plate 30 to thefoot plate 25 are each accomplished through use of a bumper assembly 35,40. The components of the bumper assemblies 35, 40 can be best observedin FIGS. 2 b and 3. As used with this prosthetic foot 5, each bumperassembly 35, 40 includes a sleeve 80, a snubber 100, a T-Nut 110 and athreaded fastener 120. In this particular embodiment, the sleeve 80 hasa cylindrical body portion 85 with a protruding flange 90. A bore 95passes through the sleeve 80. The snubber 100 is designed as a ring ofsome thickness having an axial bore 105 (see, e.g., FIGS. 10 a-10 b)sized to receive the body portion of the sleeve 80. In this embodiment,a portion of the T-Nut 110 is received in the bore 85 of the sleeve 80upon assembly, but such may not be the case in alternate embodiments.

The heel plate 30 is attached to the foot plate 25 by first placing asnubber 100 therebetween. The snubber 100 is positioned to be alignedwith corresponding heel mounting holes 125, 130 in each of the heelplate 30 and foot plate 25. The sleeve 80 is inserted through the heelplate mounting hole 125 and into the bore 105 in the snubber 100. Theflange 90 of the sleeve 80 may abut the upper surface of the heel plate30 when the sleeve is installed thereto. The T-nut 110 is inserted intothe foot plate mounting hole 130, from the underside of the foot plate25. Preferably, the foot plate mounting hole 130 includes a counter bore135 to receive the flange 115 of the T-nut 110.

In this embodiment, a portion of the T-nut enters the bore 85 in thesleeve 80. The threaded fastener 120 is then passed through the bore 85in the sleeve 80 and threaded into the T-nut 110 to secure the heelplate 30 to the foot plate 25. The threaded fastener 120 used in thisparticular embodiment of the prosthetic foot 5 is a shoulder bolt thatpermits the desired compression of the heel portion of the foot 5 duringheel strike. The shank 10 is attached to the foot plate 25 in a similarmanner, wherein the components of the toe bumper assembly 35 areinstalled through toe mounting slot 140 and toe mounting hole 145at/near the toe end of each of the shank 10 and the foot plate 25.

Each of the snubbers 100 is preferably comprised of an elastomericmaterial that allows for some compression and rebound thereof duringambulation. Consequently, the bumper assemblies 35, 40 may contribute toshock absorption during use of the prosthetic foot 5. A snubber of thepresent invention may be produced from a variety of elastomericmaterials. A non-limiting example of such a material is urethane, butone skilled in the art would realize that a number of other materialsmay also be used. Preferably, the selected snubber material has a ShoreA hardness range of between about 55 and 95, although hardness valuesoutside that range may also be possible depending on the exact design ofthe foot and/or the weight and activity level of the amputee.

A sleeve 80 of the present invention may be comprised of a rigidmaterial, such as metal or hard plastic (e.g., nylon). However, a sleeve80 may also be comprised of an elastomeric material in a manner similarto that of a snubber 100. When manufactured from an elastomericmaterial, a sleeve 80 may also contribute to shock absorption during useof the prosthetic foot 5. Adjusting the hardness, size, and/or shape ofone or more of the sleeves and/or snubbers present on a foot of thepresent invention may be practiced to best match the resultingcharacteristics of the foot to a particular amputee.

The sleeve and snubber of a given bumper assembly may be comprised ofthe same material or different materials. Similarly, the sleeve andsnubber of a given bumper assembly may be of similar or dissimilarhardness. The overall toe bumper assembly 35 and the heel bumperassembly 40 may also be of similar or dissimilar hardness (stiffness),similar or dissimilar size, and similar or dissimilar shape. Whenmultiple toe bumper assemblies are used (as described below), eachbumper assembly may exhibit a similar or dissimilar stiffness.

The use of the heel and toe bumper assemblies 35, 40 imparts theprosthetic foot 5 with several advantageous characteristics, includingthe shock absorbing characteristics described above. Further, the bumperassemblies 35, 40 also act to suspend the heel plate 30 and the footportion 20 of the shank 10 at both ends of the foot 5, thereby enablingvertical deflection thereof until one or both contact the top surface ofthe foot plate 25. Clearance holes 150 may be placed in the foot plate25 to receive a portion of the heel-to-shank retaining T-nuts 70 upondownward vertical deflection of the foot portion 20 (which acts as a toespring) of the shank 10. Alternatively, a flanged portion of theheel-to-shank retaining T-nuts 70 may be received in counter bores (notshown) placed in the underside of the heel plate 30 to prevent theirimpact against the foot plate 25.

The bumper assemblies 35, 40 may also allow for a medial or lateralleaning of the shank while still maintaining the foot plate 25 incontact with the ground. The bumper assemblies 35, 40 may further aid inpermitting movement in the anterior/posterior direction by maintaining alonger effective heel and toe spring from heel strike to toe off. Aswith the heel plate 30, one or more bumper assemblies associated with aparticular prosthetic foot of the present invention may be fieldserviceable, thereby allowing for easy customization for a particularamputee.

As shown in FIGS. 1 a and 2 b, an optional heel spring element 155 maybe located between the shank 10 and the top of the heel plate 30. Theoptional heel spring element 155 may be used to increase the springstiffness at heel strike and/or to help return more energy into anamputee's gait as the foot is moved from heel strike toward toe off. Aswith at least the snubbers 100, the optional heel spring element 155 ispreferably comprised of an elastomeric material, which may have asimilar hardness range thereto. Preferably, the heel spring element 155is also field serviceable to allow its removal or exchange with anotherheel spring element with different physical characteristics (e.g.,harder or softer or different shape). In this manner, customization of aprosthetic foot of the present invention to a particular amputee isfurther facilitated.

FIGS. 4 a-4 c illustrate a number of shanks that may be used in aprosthetic foot of the present invention. The shank of FIG. 4 arepresents the shank 10 of the prosthetic foot 5 depicted in FIGS. 1-3.The shank 10 is shown to include the toe mounting slot 140 forconnection of the shank 10 to a corresponding foot plate of a prostheticfoot. Use of the toe mounting slot 140 allows the foot portion 20 of theshank to slide in the anterior/posterior direction relative to a footplate as an associated prosthetic foot is loaded and unloaded duringambulation. As shown in FIGS. 5 a-5 b, a corresponding foot plate 160may be provided with a similar mounting slot 165 such that the shank 10and foot plate are able to move relative to one another in theanterior/posterior direction. The toe mounting slot 140 in the shank 10and the toe mounting slot 165 in the foot plate 160 may be similar ordissimilar in size. For example, one slot may be longer than the otherso as to more accurately control movement of the shank 10 relative tothe foot plate 160. The use of a mounting slot(s) allows for theadjustment of the foot compliance to meet the needs of the individualuser.

An alternate embodiment of a shank 170 that may be used in a prostheticfoot of the present invention is shown in FIG. 4 b. In this embodiment,the shank 170 includes a toe mounting hole 175 having a diameter justlarge enough to allow for passage of the corresponding sleeve element 80it is designed to receive. As such, alignment of the shank 170 with asubjacent foot plate is maintained as the prosthetic foot is loaded andunloaded during ambulation.

Another embodiment of a shank 180 that may be used in a prosthetic footof the present invention is shown in FIG. 4 c. In this embodiment, anenlarged toe mounting hole 185 is provided for connection of the shank180 to a corresponding foot plate of a prosthetic foot. The differencein diameter between the enlarged toe mounting hole 185 and an associatedsleeve is selected to be greater than that of the toe mounting hole 175shown in FIG. 4 b. The difference between the diameter of the enlargedtoe mounting hole 185 and an associated sleeve may be adjusted. The gapcreated between the enlarged toe mounting hole 185 and an associatedsleeve allows the shank 180 to slide in both the anterior/posteriordirection and medial/lateral direction relative to the foot plate as theassociated prosthetic foot is loaded and unloaded during ambulation.This feature allows for the increased movement of the shank 180 relativeto a foot plate, which increases the overall flexibility of theassociated foot.

While the shanks 10, 170, 180 shown in FIGS. 4 a-4 c are shown to have asubstantially vertical portion like the shank 10 shown in FIGS. 1-3, itis to be understood that such a vertical section may be truncated orabsent in other embodiments. Consequently, any of the shank (and/or footplate) designs represented in FIGS. 4 a-4 c, and described above, mayalso be employed in a low profile or ultra low profile prosthetic footof the present invention (described below).

Another embodiment of a prosthetic foot 200 of the present invention isillustrated in FIG. 6. This embodiment of the prosthetic foot 200 issimilar to the prosthetic foot 5 of FIGS. 1-3, except that it is a lowprofile design adapted for use with a prosthetic ankle 225. As such, theshank 205 terminates at about the height of a typical human ankle jointas it curves upward from a toe portion 210 thereof. In this particularembodiment, the shank 205 includes a pair of ankle mounting holes (notvisible) for receiving a corresponding pair of threaded fasteners orrivets that are passed through the ankle 225 and the shank. However, theshank may be adapted as necessary to receive a particular prostheticankle, and nothing herein is to be interpreted as limiting the shank touse with a prosthetic ankle like that shown herein.

The prosthetic foot 200 again includes a foot plate 215, and anintermediary heel plate 220 that are arranged and connected in themanner described above with respect to the prosthetic foot 5. The footplate 215 and heel plate 220 of this embodiment may be the same as, ordissimilar to, the foot plate 25 and heel plate 30 of the prostheticfoot 5 of FIGS. 1-3.

The shank 205, foot plate 215, and heel plate 220 of this embodiment arealso preferably comprised of materials like those described with respectto the foot 5 of FIGS. 1-3. Consequently, this embodiment of theprosthetic foot 200 offers shock absorbing and dynamic responsecharacteristics similar to the prosthetic foot 5 of FIGS. 1-3, whilebeing useable with an ankle joint and with prosthetic limbs where spaceconstraints may be an issue.

Yet another embodiment of a prosthetic foot 230 of the present inventionis illustrated in FIG. 7. This embodiment of the prosthetic foot 230 issimilar to the prosthetic foot 5 of FIGS. 1-3 and the prosthetic foot200 of FIG. 6 with respect to its use of the bumper assemblies 35, 40.However, this embodiment of the prosthetic foot 230 represents an ultralow profile design that can be used where space constraints are asignificant issue. As such, the shank of the previously described footembodiments has been eliminated from this prosthetic foot 230.

Rather, this prosthetic foot 230 includes only a foot plate 240 and anankle plate 235 that are arranged in a connected but suspendedrelationship by the bumper assemblies 35, 40, as described above. Asshown herein, the ankle plate 235 substantially mimics the curvature ofthe foot plate. In other embodiments, there may be a greater profiledissimilarity between the two plates 235, 240.

This embodiment of the prosthetic foot 230 is also designed for use witha prosthetic ankle 245, which may be of various designs. As with theshank 205 of the prosthetic foot 200 of FIG. 6, the ankle plate 235 ofthis prosthetic foot 230 may be adapted as necessary to receive aparticular prosthetic ankle, and nothing herein is to be interpreted aslimiting the shank to use with a prosthetic ankle like that shownherein.

Another embodiment of a prosthetic foot 250 of the present invention isillustrated in FIGS. 8 a-8 b. This embodiment of the prosthetic foot 250is essentially the same as the prosthetic foot 5 of FIGS. 1-3. However,this embodiment of the prosthetic foot 250 is provided to illustratethat multiple bumper assemblies may be placed at a given location. Forexample, as shown in this particular embodiment, a pair of toe bumperassemblies 35 are located between the toe portions of a shank 255 and afoot plate 260 of the prosthetic foot 250. As would be understood by oneskilled in the art, a prosthetic foot of the present invention may alsoinclude other bumper assembly combinations, such as, but not limited to,a pair of toe bumper assemblies and a pair of heel bumper assemblies, asingle toe bumper assembly and a pair of heel bumper assemblies, threetoe bumper assemblies and a single heel bumper assembly, etc. A selectedbumper assembly combination may be governed by the desiredcharacteristics of a given foot.

Another exemplary embodiment of a prosthetic foot 265 of the presentinvention is illustrated in FIG. 9. This particular embodiment sharesmany of its components with the prosthetic foot 5 shown in FIGS. 1-3.For example, this foot 265 is shown to include the same shank 10, footplate 25, and bumper assemblies 35, 40 as the prosthetic foot 5 of FIGS.1-3.

A heel plate 270 again resides between the shank 10 and foot plate 25,but its design, position and point of attachment are all different fromthe previously described foot 5 of FIGS. 1-3. In this particularembodiment, the heel plate 270 is shaped substantially like a curvedreverse “L”, wherein a substantially vertical leg of the heel platemimics the curve at the transition point of the shank 10 before turninginto a substantially horizontal leg that extends rearward for attachmentto the heel bumper assembly 40. Attachment of the heel spring 270 to theshank 10 may occur using one or more of the previously describedfastener assemblies (i.e., sleeve 55, T-nut 70, and threaded fastener75), as shown, or may be accomplished with rivets, adhesive, or variouscombinations thereof.

The thickness of the heel plate 270 may again be varied to producedifferent spring rates that can be selected according to a givenamputee's weight, gait characteristics, and/or activity level. The heelplate 270 may have a curvature that differs somewhat from that shown inFIG. 9. Nonetheless, the heel plate 270 provides for shock absorbency atheel strike, and stores and returns energy during an amputee's gaitcycle. The heel plate 270 may also permit a controlled amount ofinversion/eversion movement through twisting. In at least certainembodiments of the present invention, the heel plate 270 may be fieldserviceable, thereby allowing a prosthetist to easily interchange heelplates so as to optimize the prosthetic foot 265 for a particularamputee.

The bumper assemblies 35, 40 once again act to suspend the heel plate270 and the foot portion 20 of the shank 10 at both ends of the foot265, thereby enabling vertical deflection thereof. As explained above,the bumper assemblies are preferably placed at/near the extreme ends ofthe foot 265 so as to maximize spring length.

Various, but non-limiting, examples of potentially useable bumperassembly designs are presented in FIGS. 10 a-10 g. As shown, FIGS. 10a-10 b generally represent the sleeve 80 and snubber 100 used in thebumper assemblies 35, 40 of the previously described exemplaryprosthetic foot embodiments. The sleeve 80 and snubber 100 are shown ina substantially installed position in FIG. 10 a, and in a separatedposition in FIG. 10 b.

The remaining examples of FIGS. 10 c-10 g employ the same sleeve 80, bututilize different snubber designs. For example, the embodiment of FIG.10 c is similar to that of FIGS. 10 a-10 b, but incorporates a snubber300 of somewhat greater outside diameter. The remaining examples simplyillustrate that a snubber of the present invention may have a variety ofother shapes. For example, the snubber 305 of FIG. 10 d is substantiallyfrusto-conical; the snubber 310 of FIG. 10 e is substantiallycylindrical; the snubber 315 of FIG. 10 f is oval, which may be used toprovide a different response in the anterior-posterior directioncompared to the medial-lateral direction; and the snubber 320 of FIG. 10g is substantially hyperbolic in shape. It is to be understood thatwhile the examples depicted in FIGS. 10 a-10 g show the sleeve 80 andsnubber 100 as being separate elements, they could be combined into asingle element.

In addition to constructing a prosthetic foot of the present inventionwith bumper assemblies like those bumper assemblies 35, 40 shown anddescribed above, acceptable bumper assemblies could instead be comprisedsolely of elastomeric material, without the need for a rigid sleeve orfasteners. That is, an elastomeric material could simply be molded inplace, thereby bonding the two plates together. While it is understoodthat this design would likely eliminate the possibility of subsequentlyadjusting the dynamics of the bumper assemblies, it would also simplifythe design and reduce the cost of an associated foot.

A first exemplary embodiment of a stiffness adjustable torsion adapterfor use with a prosthetic foot of the present invention is illustratedin FIGS. 11-12. As shown, the torsion adapter 350 includes an adapterbody 355 that is adapted to attach the torsion adapter to the shank of aprosthetic foot of the present invention. In this particular embodiment,the adapter body 355 includes a cavity 360 designed to receive andretain the free end of the shank. Once the free end of the shank isinserted into the cavity 360, retention is accomplished by tightening anumber of set screws 365 on the front of the adapter body 355, whichforces an internal gibb 370 against the shank.

The interior of the adapter body 355 has an axial bore 375 (actually aseries of stepped and various shaped bores) passing therethrough. Asshown a specialized shoulder bolt 380 having upper and lower threadedsections 380 a, 380 b resides in the bore 375 and the upper threadedsection protrudes from the top of the adapter body 355. A radial bearing425 is preferably arranged over a portion of the shoulder bolt 380 toact as a rotation-permitting interface between the shoulder bolt and theinterior surface of the adapter body 355.

A series of Belleville washers 385 is passed over the lower section ofthe shoulder bolt 380 and restrained from further upward movement by itsprotruding shoulder. A thrust washer and bearing assembly 390 followsthe Belleville washers over the shoulder bolt 380. The Bellevillewashers 385 and thrust washer and bearing assembly 390 is held in placeby an adjustment housing 400 that slides over the shoulder bolt 380 andan adjustment nut 405 that is threaded onto the lower section 380 b ofthe shoulder bolt.

The adjustment housing 400 includes an internal slot 400 s that receivesa pin 380 p protruding from the shoulder bolt 380. The slot and pinarrangement allows the adjustment housing 400 to move vertically alongthe length of the shoulder bolt 380, while also serving to couple theadjustment housing to the shoulder bolt so that the two components willrotate in tandem (as described in more detail below). A radial bearing415 is preferably located between the exterior of the adjustment housing400 and the interior wall of the adapter body 355 to facilitate rotationof the adjustment housing therein. Rotation of the adjustment housing400 is also facilitated by the thrust washer and bearing assembly 390,which permits rotation of the adjustment housing relative to theBelleville washers 380.

The adjustment nut 405 threads onto the lower section 380 b of theshoulder bolt 380 and travels up into the adjustment housing 400. Theadjustment nut 405 may have a hex broach or may be otherwise adapted foreasy adjustment with a hex wrench or other tool. A retaining ring 410 ora similar element may be used to prevent the unintended loosening orremoval of the adjustment nut 405. Tightening of the adjustment nut 405will eventually exert a preload on the Belleville washers 385 by forcingthe adjustment housing 400 upward into the adapter body 355. The preloadof the torsion adapter 350 can, therefore, be adjusted via theadjustment nut 405 to allow the amount of resistance to rotationexhibited by the torsion adapter to be customized for each amputee.

An upper portion 355 a of the adapter body 355 is shaped to fit withinthe receiving cavity 445 of what may be referred to as a pyramidreceiver 440 (a term that would be well known to one skilled in theart). The upper portion 355 a is provided with a ramped top surface,that mates with the ramped underside of a crown element 420 that reststhereon. As explained in more detail below, this arrangement results inan increase in the overall length of the torsion adapter 350 duringrotation. A radial bearing 430 or similar device may be located betweenthe exterior of the upper adapter body portion 355 a and the wall of thepyramid receiver cavity 445 to facilitate rotation therebetween.

The pyramid receiver 440 is affixed to the torsion adapter 350 byengaging a threaded bore 450 in the pyramid receiver with the protrudingand like-threaded upper section 380 a of the shoulder bolt 380.Preferably, the pyramid receiver 440 is also affixed to the crown 420 bydowel pins 435 or other fasteners to prevent rotation of the crownrelative to the pyramid receiver.

The pyramid receiver 440 is provided to attach the torsion adapter 350to the remainder of a prosthesis, preferably using industry standardpyramid components. The pyramid receiver 440 also provides for angularalignment of a prosthetic foot of the present invention relative to thesocket of a prosthesis, and supports radial loading during ambulation.As described below, a prosthetic pyramid could be substituted for thepyramid receiver 440.

Operation of the torsion adapter 350 will be explained in the context ofan assembled torsion adapter being attached to the shank of a prostheticfoot, and the foot/torsion adapter assembly connected to a prostheticsocket of a prosthesis by the pyramid adapter 440 and an associatedpyramid. During use of such a prosthesis, rotation of the pyramidreceiver 440 (via the pyramid) will cause a corresponding rotation ofthe crown 420. As rotation occurs, the opposing ramps of crown 420 andupper portion 355 a of the adapter body cause the torsion adapter 350 toincrease in length. As the torsion adapter increases in length, theBelleville washers 385 are compressed, thereby increasing the resistanceof the torsion adapter 350 to rotation. The opposing ramps of the crown420 and adapter body 355, along with the forces generated by theBelleville washers 385 and the weight bearing load of an amputee, willforce the torsion adapter 350 to always return to its neutral position.The resistance to rotation may be adjusted and the overall amount ofrotation may be controlled by varying the thickness, stack height,and/or stack orientation of the Belleville washers 385.

An alternate embodiment of a torsion adapter 500 of the presentinvention is depicted in FIG. 13. As shown, the torsion adapter 500 isvery similar to the torsion adapter 350 described above, except that apyramid adapter 455 has been substituted for the pyramid receiver 440thereof. The remaining elements of the torsion adapter 500 may be thesame as described above, and the pyramid adapter 455 may be attached tothe adapter body 355 in a like manner.

While certain embodiments of the present invention are described indetail above, the scope of the invention is not to be considered limitedby such disclosure, and modifications are possible without departingfrom the spirit of the invention as evidenced by the following claims:

What is claimed is:
 1. A prosthetic foot, comprising: a shank having asubstantially vertical portion graduating into a curved foot portion; afoot plate; a heel plate connected to said curved foot portion of saidshank and extending rearward therefrom; a toe bumper assembly connectinga toe end of said shank to a toe end of said foot plate; and a heelbumper assembly connecting a rearward end of said heel plate to a heelend of said foot plate; wherein said shank and said heel plate are heldin a suspended position above said foot plate by said toe and heelbumper assemblies.
 2. The prosthetic foot of claim 1, wherein said heelplate is connected to an underside of said foot portion of said shank.3. The prosthetic foot of claim 1, wherein a heel portion and toeportion of said foot plate are curved.
 4. The prosthetic foot of claim1, wherein each bumper assembly includes an elastomeric element thatacts to absorb shock and return energy to an amputee's gait duringloading and unloading of said prosthetic foot.
 5. The prosthetic foot ofclaim 1, wherein said foot plate acts as a hard stop to downwarddeflection of said shank and said heel plate during loading of saidprosthetic foot.
 6. The prosthetic foot of claim 1, further comprisingan elastomeric element located between an underside of said shank and atop surface of said heel plate.
 7. The prosthetic foot of claim 1,wherein said toe bumper assembly includes separate sleeve and snubberelements, said snubber element residing between said foot plate and saidshank, and said sleeve element passing through a mounting hole in saidshank and into a bore in said snubber.
 8. The prosthetic foot of claim7, wherein one or both of said sleeve and snubber elements is comprisedof an elastomeric material.
 9. The prosthetic foot of claim 7, furthercomprising a T-nut passing through a mounting hole in said foot plateand a threaded fastener passing through a bore in said sleeve element,said threaded fastener engaging a like threaded section of said T-nut tosecure said foot plate to said shank.
 10. The prosthetic foot of claim1, wherein said heel bumper assembly includes separate sleeve andsnubber elements, said snubber element residing between said foot plateand said heel plate, and said sleeve element passing through a mountinghole in said heel plate and into a bore in said snubber.
 11. Theprosthetic foot of claim 10, wherein one or both of said sleeve andsnubber elements is comprised of an elastomeric material.
 12. Theprosthetic foot of claim 10, further comprising a T-nut passing througha mounting hole in said foot plate and a threaded fastener passingthrough a bore in said sleeve element, said threaded fastener engaging alike threaded section of said T-nut to secure said foot plate to saidheel plate.
 13. The prosthetic foot of claim 1, further comprising atorsion adapter attached to said substantially vertical portion of saidshank, said torsion adapter for connecting said prosthetic foot to theremainder of a prosthesis.
 14. The prosthetic foot of claim 16, whereinsaid torsion adapter includes a pyramid receiver or a pyramid.
 15. Aprosthetic foot, comprising: a shank having a substantially verticalportion graduating into a curved foot portion; a foot plate having acurved heel and toe portion; a heel plate connected to and extendingrearward from an underside of said foot portion of said shank; a toebumper assembly connecting a toe end of said shank to a toe end of saidfoot plate, said toe bumper assembly including a sleeve, elastomericsnubber, and T-nut, said snubber residing between said foot plate andsaid shank, said sleeve element passing through a mounting hole in saidshank and into a bore in said snubber, and said T-nut passing through amounting hole in said foot plate, such that a threaded fastener ispassed through a bore in said sleeve to engage a like-threaded sectionof said T-nut to secure said foot plate to said shank; a heel bumperassembly connecting a rearward end of said heel plate to a heel end ofsaid foot plate, said heel bumper assembly including a sleeve,elastomeric snubber, and T-nut, said snubber residing between said footplate and said heel plate, said sleeve element passing through amounting hole in said heel plate and into a bore in said snubber, andsaid T-nut passing through a mounting hole in said foot plate, such thata threaded fastener is passed through a bore in said sleeve to engage alike-threaded section of said T-nut to secure said foot plate to saidheel plate; wherein said shank and said heel plate are held in asuspended position above said foot plate by said bumper assemblies. 16.The prosthetic foot of claim 15, wherein said foot plate acts as a hardstop to downward deflection of said shank and said heel plate duringloading of said prosthetic foot.
 17. The prosthetic foot of claim 15,further comprising an elastomeric element located between an undersideof said shank and a top surface of said heel plate.
 18. The prostheticfoot of claim 15, wherein at least one sleeve is comprised of anelastomeric material.
 19. The prosthetic foot of claim 15, furthercomprising a torsion adapter attached to said substantially verticalportion of said shank, said torsion adapter for connecting saidprosthetic foot to the remainder of a prosthesis.
 20. The prostheticfoot of claim 19, wherein said torsion adapter includes a pyramidreceiver or a pyramid.